Electric Pre-Rotator

All_In

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San Diego, CA. USA
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Piper Archer, Aviomania G1sb
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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
The good news is the jump-takeoff team has designed all the components. Only the machine class professor told them no way students can machine, assemble, test, make changes and final test in only 6 months.

Dick Degraw helped and the engineering students spend 3 mounts before final design evaluating electric, hydraulic, and back to power takeoff considering cost and weight to performance with data that show it all for anyone to follow!
 

All_In

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Joined
Apr 21, 2008
Messages
14,665
Location
San Diego, CA. USA
Aircraft
Piper Archer, Aviomania G1sb
Total Flight Time
Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
A note on cheap batteries. I'm building them myself.
I buy used laptop battery packs and break them open and remove the batteries they cost about a dollar each, not $5 to $10 for the best new ones. Many still maintain full capacity and voltage of 4.2 volts.
All you have to do is charge them all up and measure the voltage they hold.
Just make all the batteries are the SAME voltage in each BATTERY and any cheap $3 controller will charge the entire pack but not uneven voltage the excess available in all other individual batteries will only charge to the lowest voltage battery.
The photo is how I test them before I solder the real one together forever. This one cost less than $45.
This kit lets you build a temp battery for testing in minutes using nuts and bolts.
This one has forty 4.1-volt batteries it will be 16 volts and 1/2 of a 32-volt battery pack consisting of two of these in parallel. Each with its own charge controller.

After testing I solder house AC wire striping it first and fold it in half to the exact length I need. Then clamp it in a vice and twist it into one thicker wire. If you don't have a spot welder use a VERY BIG and HOT soldering iron tin the wire first.
Then you connect them in series with a thin wire that will blow like a fuse if over the max amps any one cell should be drawing if not defective. Like Tesla does.
Then just a fraction of heat on the battery on the thin wire linking all cells in series and parallel
Note: Heat can destroy batteries. They can explode with a small low temp iron as it will take so long to transfer the heat.

Here is the quick build kit for testing. https://vruzend.com/ Although people do use them in production. It cost more than house wire.
BatteryPack.jpg
 

All_In

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Joined
Apr 21, 2008
Messages
14,665
Location
San Diego, CA. USA
Aircraft
Piper Archer, Aviomania G1sb
Total Flight Time
Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
PRA will make kits available in our future.
 

JETLAG03

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Jul 6, 2019
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56
Location
Virollet 17260 FRANCE
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300+ flexwing (pendulaire) newly trained on gyrocopter (autogire)
@All_In look forward to your results etc .

Just checked the starter motor used for my pre-rotator and found it to be a real wimp 0.9kw. There are available high torque starters and I'm guessing some-one has already tried, tested and rejected these starters for one or more reasons ie too aggressive on startup, weight or other reasons .... is this so chaps?

phil
 

jm-urbani

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Dec 21, 2010
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French Riviera
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home built mono seat
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200ish
it seems that you will test your electric barbecue before me ... hhahaha ( I am kiding) it is great to see things going ahead
 

DarDow101

Dar
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Jun 11, 2017
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Location
Utah
it seems that you will test your electric barbecue before me ... hhahaha ( I am kiding) it is great to see things going ahead
It does kind of look one of those exploding devices.....and the batteries are lithium ion after all.... not thrilled about that but Kolbalt is using the best quality batteries...Panasonic 18650's.
 

wolfy

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Dec 19, 2013
Messages
181
Location
western australia
Well done so far mate will be interesting to see the results, I can't remember if you said already but what Rrpm are you expecting and what size rotor and how many watts is your motor?

wolfy
 

DarDow101

Dar
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Well done so far mate will be interesting to see the results, I can't remember if you said already but what Rrpm are you expecting and what size rotor and how many watts is your motor?

wolfy
Rrpm ~ 200+
Rotor Size = 25' Skywheel's
Motor - 2000W 40-60 Amps / 12-48V DC 4.5 HP
 

wolfy

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western australia
That video was 3 years ago. At that time I used a knob for control. Now I have 3 buttons and a micro controller. off/reset, Idle, where it takes it from a few RPM to idle speed of 65 RRPM, and fly, taking it from idle to full RRPM. I've seen 215 RRPM peak but it pulls past that. I use between 375-500 milliamp hours for a complete spin up. idle, taxi at idle, and full prerotation, so, between 6 and 10 full prerotations for the batteries I use. I'm working with Denis at Gyrotechnic to fit it to his rotorhead. After I do that I'll work on fitting it to existing Wunderlich heads.
Hi John could you share anymore info on your set up,
2300w?
How many Kv?
What is your total reduction ratio from motor to rotor?
Rotor diameter?
Currently designing and just comparing notes.

thanks wolfy
 

Sv.grainne

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Jan 14, 2020
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Location
Kerrville, Texas
You provided specs on the motor, 2000W 40-60 Amps / 12-48V DC 4.5 HP, but wondering what voltage you are using for your test setup? How long from a dead stop to suitable rotor speed??

Bobby
 

DarDow101

Dar
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Jun 11, 2017
Messages
63
Location
Utah
You provided specs on the motor, 2000W 40-60 Amps / 12-48V DC 4.5 HP, but wondering what voltage you are using for your test setup? How long from a dead stop to suitable rotor speed??

Bobby
12V 24V 36V and now 40V tested and rotor "real world" Rrpm TBD.
 

jm-urbani

Junior Member
Joined
Dec 21, 2010
Messages
480
Location
French Riviera
Aircraft
home built mono seat
Total Flight Time
200ish
It does kind of look one of those exploding devices.....and the batteries are lithium ion after all.... not thrilled about that but Kolbalt is using the best quality batteries...Panasonic 18650's.
hooo yes your right ... I will be charging the lipos today .. and do the wiring
 

DarDow101

Dar
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Jun 11, 2017
Messages
63
Location
Utah
Saw your last post but no way to tell what you are doing or what the conditions were. Multi voltage motor but what were the conditions of you last test where you stated ah draw in the battery bank.
i guess i don't understand your questions. I tested the motor and controllers from 12v up to 40 volts to be sure everything was working good as configured and i have not tested ah draw on the batteries since i haven't tested what it will do with rotors being spun up. if it does that effectively that's all i care about. I will worry about capacity after it spools up my rotors to 200 rrpm or not. As far as conditions go not sure what you mean....weather, temps, calm winds?
 

wolfy

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Joined
Dec 19, 2013
Messages
181
Location
western australia
I have just found a few more motor suppliers, some very powerful motors.
Alien power systems.com
Freerchobby.com

I am still trying to get my head around Kv values, I understand that a lower kv will mean higher torque at a lower speed.
But in our situation we are trying to get to a given rrpm, so a lower kv motor will need less reduction to the Bendix than a higher kv motor meaning the torque applied to the Bendix will be the same.
So for our application is the Kv value of any real importance, given that the total reduction will be adjusted to suit target rrpm?
Meaning that the kw value is really the only one of use?

wolfy
 
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